Fundamentals 03
CRI & R9
How faithfully a light source renders colour compared to a reference source.
CRI (Colour Rendering Index) is a 0–100 score averaged across eight pastel test colours. R9 is a separate score for saturated red. Both matter — CRI 90 alone does not guarantee good red rendering.
For gallery, museum, hospitality and retail lighting, specify CRI ≥ 90 and R9 ≥ 90. For general spaces, CRI ≥ 80 is acceptable.
Poor CRI shows up on skin, food, and warm pigments. It cannot be corrected by dimming or filtering.